Ankle joint for artificial limbs



s. A. WlLLETT 2,066,599 JOINT FOR ARTIFICIAL LIMBS Patented Jan. 5, I937UNITED STATES,

2,066,599 ANKLE JOINT FOR ARTIFICIAL LIlVIBS Samuel A. Willett, Paducah,Ky., assignor. of

one-half to Birmingham Artificial Limb Company, Birmingham, Ala., acorporation of Alabama Application July 18, 1935, Serial No. 32,003

14 Claims.

My invention relates to certain new and useful improvements in an anklejoint for artificial limbs, my object being to provide a joint in whichthe articulated joint elements are held in engagement by an elastic bodyof substantial mass which is brought under initial compression by themanner of assembling the ankle element and which permits both verticalplay and limited universal angular play between the shin member and thefoot piece.

My invention contemplates the provision of a substantially cylindricalor barrel shaped resilient body to occupy the axis of the ankle jointand v I be interposed between the interlocked metallic joint members anda limb element in such manner as to form a resilient support for theshin piece which provides both for vertical and angular play of thefoot, 'the elastic body being so 4 L shaped and held under compressionbetween seats on the shin and foot pieces as to exert a resilient effectthat cooperates with the standard elastic foot pads in restoring andmaintaining the normal relationship between foot and shin piece when thelimb is at rest. More particularly, my invention contemplates theprovision'o-f an elongated barrel shaped solid cushion member, which hasapproximately a one inch diameter at the center so as, to provide asubstantial mass of elastic material in the middle portion of the anklejoint, the tapering of this body'toward the ends being desirable toprovide for the requisite universal play at the ankle joint Withoutundue pressure on the body at any point i. that will allow the footpiece to rock from side to '35 side at any angle with sufiicientfreedomfor comfort. l

My invention further contemplates interposing such an axial cushion bodyas is described in the m preceding paragraph between a saddle extending40 transversely across the ankle joint and attached preferably to theshin piece, a U-bolt being mounted astride this saddle and connectedtothe foot in the longitudinal center plane, this U-bolt acting both tomechanically couple the foot and shin piece and compress the cushionbody in such manner and position as to allowthe desired limiteduniversal motion for the foot.

My invention further contemplates as an added feature of importance thatthe axial cushion body as it becomes compressed as the weight comes onthe ankle joint will cause a sufficient separation of the coupledmetallic joint elements so that the Wearers Weight will floaton thecushion 5 member and in reality there is no appreciable frictionalengagement between the metallic elements in the normal play of the foot.

Myinventio-n, which I have shown only in its preferred embodiment butwhich may be variously modified Without departing from its novelprinciples of construction, will be best understood by reference to theaccompanying drawing, in which: i

Fig. 1 is a vertical central longitudinal section through the foot andshin piece assembled by 10 my improved ankle joint.

Fig. 2 is a transverse section through the foot showing the saddle inside elevation with its studs broken away.

Fig. 3 is a detail cross section of the seat por- 15 tion in'the footpiece for the elastic body shown in dottedlines.

Fig. 4 is a detail view of the axial cushion body. Similar referencenumerals refer to similar parts throughout the drawing. 20

In the preferred embodiment of my invention illustrated, I showconventionally a shin piece 5 having its ankle portion ii of usualcontour and adapted to be received in the top recess 1 in the foot 8 andthere to rest in the usual manner upon 25 the instep cushion 9 and theheel bumper Hi, the latter being reduced in size and seated in avertical recess II in theheel. In the foot piece I provide astraight'transverse bearing seat l2 ex- 7 tending entirely across thefoot piece and struck 0 on an are substantially coaxial with thetransverse axis of the ankle joint In the longitudinal central plane ofthe foot, on each side of this bearing I2, I provide openings throughwhich the threaded shanks of U-bolt it are adapted to be passeddownwardly and forwardly through the foot so that the U-bolt lies in avertical central longitudinal plane through the foot.

The threaded ends of the U-bolt project into the bottom recess M in thefoot and receive metal 40 lock washers l5 and nuts it by which theU-bolt is tightened up to couple the foot and shin pieces.

I mount transversely across the underface of the ankle portion 5 oftheshin piece an arcuate shaped saddle plate H, the exterior contour ofwhich conforms substantially to the inner arc .of the bend in the U-boltl3 and this saddle piece is provided at its center on top with spacedraised elements l8 which form a seat to receive the U-bolt l3 on top soas to prevent transverse displacement between the saddle and the U-bolt,these elements it being flared apart as they approach the side edges ofthe saddle so as to ofier no resistance to a limited universal angularplay of the U-bolt l3 as it responds to the play of the foot.

This saddle l1 carries on each side of the bolt seat elements I 8, I8 avertical attachment stud 19, these studs lying in a transverse axialplane and extending upwardly through the solid lower end 6 of the shinpiece into the recess therein where they are passed through lock washers20 and made fast by the nuts 2|.

The ankle element 6 is formed with a seat that extends transverselyacross the ankle joint and conforms to the shape of the saddle elementsI! and i8, being additionally recessed to receive the U-bolt l3 with aloose fit that provides clearance for both vertical and angular play forthe U- bolt l3 relative to the saddle.

The most important feature of my invention consists in the elastic orresilient body 23 that is interposed axially of the ankle joint betweenthe seat l2 in the foot and the saddle I! on the shin. This body haspreferably a barrel-like shape and I have obtained excellent resultswith a body composed of best grade elastic rubber and having a diameterof one inch at its center tapering to 'V ths of an inch at each end.While it is not essential, it is preferable that the element be reducedin diameter toward the ends as thereby to free the joint better for thelimited universal play of the foot that is so essential for full walkingfreedom. This axial elastic body 23 is set into the foot seat l2 withthe saddle piece I! resting on it and the U-bolt l3 astride it and thesaddle. The parts as shown thus assembled in Fig. l and to set up thejoint, the nuts 2| are tightened fully to lock the saddle in position onthe shin piece and the nuts l6 are tightened to draw the U-bolt I3against the saddle and the saddle against the elastic body 23 so as toput it under the desired initial pressure between the seat l2 and thesaddle.

It is desirable to bring this elastic body 23 under substantial initialcompression, this being determined empirically according to the comfortof the individual wearer. With the ankle joint thus assembled, it willbe apparent that the foot and shin are interlocked by the directengagement between the metallic elements l3 and I1 and so held that whenthe wearers weight comes on the joint the shin piece will float on theinterposed elastic body 23. The shin piece is designed so that theU-bolt I3 is held by the interposed body 23 in contact with the saddleI! while provision is made in the ankle portion of the shin for theU-bolt to have a limited vertical play requisite for the floatingsupport of the shin and also angular play relative to the saddle toallow the foot free motion about the center of the ankle joint as anaxis. It will be apparent when the full weight of the wearer comes uponthe elastic body 23 its further compression will ease the engagementbetween the U-bolt and the saddle and will thus leave the foot piecefreer to float, but the space in which the U-bolt l3 works does notpermit it to move vertically far enough away from the saddle to produceobjectionable noise in the joint. Preferably, the elastic body 23extends substantially the full width of the ankle element 6, thusproviding an ample elastic support both at the center and at the sidesof the foot.

It will be noted that the compression on this elastic member is greatestat the center and least at its ends. This tends to free the foot piecebetter for limited universal angular play without imposing unduecompression on any part of the elastic body 23 which would tend torapidly destroy its resiliency.

In my ankle joint the heavy duty imposed when the weight of the weareron the heel and toe of the foot is taken by the engagement between themetallic coupling elements with the resilient body 23 at rest except forits initial compression but when the direct load comes on the anklejoint the weight of the wearer shifts onto the resilient body and themetallic elements are freed, leaving the foot free for its limiteduniversal play. While it is preferable that the metallic elements berespectively connected as shown to the foot and shin piece suchconnection is obviously reversible without material change in function.

While I have shown my invention in but one form, it will be obvious tothose skilled in the art that it is not so limited, but is susceptibleof various changes and modifications, without departing from the spiritthereof, and I desire, therefore, that only such limitations shall beplaced thereupon as are imposed by the prior art or as are specificallyset forth in the appended claims.

What I claim is:

1. In an artificial limb, an ankle joint comprising a shin member, afoot member, a body of resilient material occupying the axis of theankle joint and extending transversely across same, a metallic saddlefitted lengthwise on said body and secured to one of said members, and aU-bolt astride said saddle and body and connected to the other memberfree for articulation relative to said saddle and the member to whichthe saddle is secured.

2. An artificial limb according to claim 1, in which the saddle issubstantially coextensive with the axis of the ankle joint and ismounted free for angular play on said resilient body.

3. An artificial limb according to claim 1, in which the saddle isarcuate and said resilient body is rounded to fit the saddle andelongated to extend approximately across the ankle joint.

4. An artificial limb according to claim 1, in which the resilient bodyis elongated and tapered toward its ends and extends axially of theankle joint under initial compression between said saddle and thediametrically opposed limb member.

5. In an artificial limb, the combination with a shin piece and a foot,of two metallic elements to couple said shin and foot at the ankle jointfree to articulate, means to cause said elements to engage and take thefull leverage thrust applied at the ankle joint from weight of thewearer on the toe of the artificial foot, and an elastic elementinterposed in the ankle joint in position to hold said metallic elementsnormally engaged and adapted to yield and free said elements so as toform an elastic support for the load applied vertically on the joint.

6. An artificial limb according to claim 5, in combination with anelastic instep bumper interposed between the toe and the ankle joint toform a resilient fulcrum for yieldingly supporting the load on the toeportion when said metallic elements are engaged.

7. An ankle joint construction for artificial limbs, comprising aU-bolt, a saddle adapted to fit into the bight of said bolt free toarticulate and having means to anchor it to a limb member, and a rubbercushion adapted to be received between the saddle and the limb member towhich the U-bolt is attached.

8. An ankle bolt construction for artificial limbs, comprising a U-bolt,a saddle adapted to fit into the bight of said bolt free to articulateand having means to anchor it to a limb member, and a rubber cylinderadapted to fit between the legs of the U-bolt against concave seatsinsaid saddle and the opposed limb member.

9. An artificial limb comprising shin and foot members, metallicelements which are interlocked at the ankle joint to couple said membersfree for relative vertical and angular play, and a resilient memberinterposed axially of the ankle joint in position yieldably to hold saidelements engaged and, as it becomes compressed under downward pressureat the joint, to free said metallic elements by relative movements in avertical plane from engagement and become the sole support at the jointaxis for the wearers weight.

10. An artificial limb comprising shin and foot members, metallicelements which are engaged to couple said members for relative verticaland angular p1ay, and a resilient member mounted under initialcompression along the joint axis in position normally to hold saidelements engaged and adapted to yield under the wearers weight to freesaid metallic elements for relative vertical displacement, thereby tosupport the wearers weight transmitted through the ankle joint on tosaid resilient member and leave the shin member riding said resilientmember free for limited universal angular play thereon.

11. An artificial limb according to claim 1-0, in which the yieldingmember at the ankle joint is elongated to extend substantially acrossthe joint and is reduced in thickness toward its ends.

12. An artificial limb comprising shin and foot 7 members, metallicelements which are engaged to couple said members for relative verticaland angular play, and a resilient member interposed axially of the jointin position as it yields under pressure at the joint to free saidmetallic elements to separate vertically and thereby transmit thewearers weight through the ankle joint onto said resilient member, saidmember being elongated and disposed substantially coextensive with theaxis of the ankle joint.

13. An ankle joint construction for artificial limbs, which comprises incombination with shin and foot members. a U-bolt connected to one memberover a concave seat therein extending transversely of the joint, arubber cylinder in said seat, a saddle engaging the cylinder opposite tosaid seat and connected to the other member, said saddle being heldagainst the bight of said U-bolt by the elastic resistance of saidcylinder when the foot is at rest and being free to move relative tosaid U-bolt as said cylinder yields responsive to the weight of thewearer on said joint.

14. In an ankle joint for the foot and shin members of an artificiallimb, metallic elements secured to said members and adapted to interlockthem free for articulation and relative vertical movement between saidmembers, a transversely elongated elastic body mounted under compressionin the ankle joint and adapted yieldingly to resist verticaldisplacement and angular play between foot and shin, and an elasticbumper interposed between the foot and shin members on the toe side ofsaid compression member and adapted to supply the yielding support whenthe metallic elements interlock to resist the leverage applied by theweight of the wearer on the toe of the foot,

SAMUEL A. WILLE'IT.

